More Short Term Pain in Noncemented Total Knee Arthroplasty: A Matched Cohort Analysis

Despite the resurgence of noncemented total knee arthroplasty (TKA) following implant advancements in recent years, instances of greater postoperative pain remain a common finding compared with TKAs with cemented fixation. Newer noncemented designs have become appealing to younger, heavier, and active patients, with appropriate bone stock.

A matched cohort analysis of patients undergoing primary, unilateral cemented and noncemented TKAs at a high-volume, orthopaedic specialty hospital. Enrolled patients had their index procedure between March 1, 2020, and December 31, 2023. The initial cohort was 4,275 patients, with 455 noncemented and 3,820 cemented TKA patients. Patients were matched 1:1, with MAKO instrumentation and sex being matched exactly, while age was matched within 2 years, yielding 229 patients per group. Patient-reported outcomes were completed preoperatively, at 12 weeks, 6 months and 1 year. Forgotten Joint scores were assessed at 1 year.

Patients' reported pain levels during their inpatient stay were higher in noncemented TKA patients, with pain values of 3.1 (±1.5) versus 3.2 (±1.7) at rest ( P = 0.397) and 4.4 (±1.6) versus 4.8 (±1.8) with activity ( P = 0.031). Morphine Milligram Equivalents were 26 points higher in the noncemented group (101.4 vs. 75.0, P < 0.001). Knee Injury and Osteoarthritis Outcome Scores for Joint Replacement were similar between cohorts at all time points, when adjusted for preoperative differences. Forgotten joint scores were significantly different with the noncemented group scoring lower (56.6 [±28.2] vs. 44.3 [±31.7], P = 0.013) and fewer patients met the threshold for forgetting their joint (75.3% vs. 51%, P = 0.002). Complications and readmissions were similar between groups.

This study concludes that noncemented TKA patients experience greater early postoperative pain and are more likely to be aware of their prosthesis than cemented TKA patients. Morphine Milligram Equivalent utilization for noncemented TKA patients was also markedly higher. Future studies should examine how to best define success for noncemented TKAs.